Chemical treatment and packaging process to improve the appearance and shelf life of fresh pork

ABSTRACT

A process for packaging fresh pork and the fresh pork package having enhanced visual appeal and shelf life stability, the process including the steps of introducing into the pork a treatment solution comprising a lactate buffer salt, a phosphate sequestrant and a diacetate flavor enhancement agent, and packaging the pork in a display unit. The display unit can comprise a thermoplastic tray covered by a transparent film and further packaging one or more display units in a film wrapped container. The atmosphere within the container can be maintained as a high oxygen atmosphere.

FIELD OF THE INVENTION

The invention relates to an improved packaged fresh pork and processesfor packaging the pork. The fresh pork is treated with an aqueoussolution and packaged in a display unit. Such a unit can be shipped in amaster container such as a master bag or container or master conformingbox. The resulting pork product can be processed and transported from apacking house directly to a retail outlet where the pork in the displayunit can be displayed for retail sale in a retail case. At the retailoutlet the display unit is removed from its master bag or conforming box(if necessary) and is placed in a display cooler. The cooperationbetween atmosphere, packaging and treatment provides an improved porkproduct. Further, a selected packaging atmosphere and a related packagesystem can improve the quality and consumer acceptance of the pork andto improve its shelf life.

BACKGROUND OF THE INVENTION

The treatment and packaging of fresh pork has been a subject of intenseresearch and development for many years. A variety of fresh porktreatment chemicals, packaging atmospheres and packaging materials areknown. A vast variety of chemical treatment materials or pumpingsolutions have been used including sugar, salts, curing compounds,ascorbate, isoascorbate, etc. A useful atmosphere can contain varyingproportions of inert gases such as argon, nitrogen, etc., red pigmentforming gases such as oxygen, carbon monoxide and other gases such ascarbon dioxide. Many such atmospheres have been evaluated in conjunctionwith a number of packaging systems. Pork packaging has been made frommany types of packaging materials including paper, paperboard,corrugated paperboard, film, metallized film, foam plastic and rigidplastic wrap, etc.

We are aware of certain patents that generally teach a variety of meatpacking systems. Vaughan, U.S. Pat. No. 3,047,404, teaches a packagingsystem for red meats. The meat is packaged in a film wrapped containerwhich is then stored in a transportable rigid, box-like container havinga high oxygen atmosphere. Voegeli et al., U.S. Pat. No. 3,154,421,discloses that a desirable bright red fresh meat color can be enhancedand maintained for about seven days if fresh meat is packaged in theambient atmosphere. The meat is contacted with a treatment solutioncomprising phosphate salts, ascorbic acid or salts thereof and asequestrant agent. Lugg et al., U.S. Pat. No. 3,851,080, teach freshmeat maintained in a controlled atmosphere containing a majority ofcarbon dioxide, a smaller amount of molecular oxygen, the balance beingnitrogen. Preferred atmospheres contain between 10 and 40 vol % carbondioxide, 12 and 20 vol % oxygen and 50 to 70 vol % nitrogen. Ferrar etal., U.S. Pat. No. 4,642,239, teach a package having a controlledatmosphere having a high oxygen concentration. Ferrar et al. teach aunique packaging system having a film having an oxygen permeabilityhigher than its carbon dioxide permeability. Such a packaging systemensures that the oxygen content inside the container remains high tomaintain the fresh red appearance of the meat. Cheng, U.S. Pat. Nos.4,683,139 and 4,818,548, teaches a process for prepacking fresh meat,enhancing and improving the consistency of the meat quality at the pointof retail sale and to increase the shelf life of meat. In the Chengpackage, chemically treated meat is packaged in a controlled atmospherecontaining 20-80% carbon dioxide and from about 2-30% oxygen, anybalance is nitrogen. The treatment solution contains active componentsincluding certain phosphate compounds, a reducing agent and an organicsequestrant such as citric acid, tartaric acid, EDTA, etc. Schvester etal., U.S. Pat. No. 4,946,326, teach seafood packaging using anatmosphere having a substantial portion of inert gas such as nitrogen orargon, 50 vol % carbon dioxide and 20 vol % oxygen.

Prior art processes are costly, can be complex and often serve to merelymask spoilage and not prevent microbial growth. A substantial needexists to improve the fresh meat packaging technology relating tosubstantially preventing microbial growth in fresh pork productsincluding bone-in products and bone-free products such as halfcarcasses, whole loins, roasts, cuts, chops, ground pork, etc. Asubstantial need exists to obtain tender cut pork portions, to maintaina quality of appearance and shelf stability of cut meat and to reducepurge in a simple easily used packaging system using a treatmentsolution and packaging. A substantial need exists to provide a producthaving an extended shelf life and an attractive fresh red meatappearance, while maintaining high quality flavor, stabilizedmicrobiology, tenderness and consumer acceptance that is low in cost andeasily implemented with a chemical treatment, packaging system andatmosphere.

BRIEF DISCUSSION OF THE INVENTION

We have found that the appearance measured by color and freedom frompurge, shelf life including reduced microbial growth, texture andtenderness of the cut meat portions and cooked flavor of the fresh meatcuts can be enhanced by a cooperation between atmosphere, packaging andtreatment chemicals. The treatment chemicals include a component that isa flavor enhancer and an antimicrobial, a phosphate or condensedphosphate sequestrant composition and a diacetate microbial growthinhibitor component. The unique process includes first treating the meatwith an aqueous treatment solution containing a sodium lactatecomposition, a phosphate sequestrant composition and an alkali metaldiacetate microbial growth inhibitor or retardant. Such treated meat canbe cut or sliced, if needed and can be packaged in a display unitcomprising a film wrapped package, or display unit, for a retail case.Such display units can, in turn, be packaged for transportation,distribution and presale storage in a sealed master container or bag.

An enhanced oxygen atmosphere can be used with the disclosed packaging.The product configuration can comprise a display unit that is flushedand filled resulting in a high oxygen atmosphere. The high oxygenatmosphere in the package can comprise about 50-85 vol % oxygen andabout 15-30 vol % carbon dioxide. Preferably the high oxygen atmospherecomprises about 60-80 vol % oxygen and less than about 20 vol % carbondioxide. Such a high oxygen atmosphere is provided by filling thedisplay unit with an artificial atmosphere comprising greater than 85mole %, preferably 90-100 mole % O₂. In the instance the display unit isshipped directly to a retail outlet, the film used in making the displaypackage can comprise an oxygen barrier film to maintain the oxygenatmosphere within the display unit. In the instance that the displayunit is packaged in a master container or master bag system containingan oxygen atmosphere, the display is typically packaged in an oxygenpermeable film to ensure that any oxygen consumed inside the package canbe replenished by oxygen from the atmosphere within the master bag orcontainer that contains the display units. At the retail outlet, themaster bag or container is opened and the display units are removed forretail display.

For the purpose of this patent application the term "oxygen barrier" or"oxygen barrier film" relates to a film or other useful packagingmaterial that retains oxygen. Such a barrier preferably prevents thepermeation of oxygen through the film and out of the package at a ratesuch that the internal atmosphere of the packaging material loses lessthan about 8 to 10 vol % of oxygen during the product shelf life(typically less than about 30 days) to transport of oxygen through thebarrier. Similarly a "CO₂ barrier" prevents movement of CO₂. Oxygen canbe consumed through absorption by the meat or by bacterial growth. Theoxygen barrier bag has an oxygen permeability of less than about 200cc-O₂ /m² •day•atm @73° C.; preferably less than 145 cc-O₂ /m² •day•atm@73° C. CO₂ barrier materials have similar numbers for CO₂ filmproperties. The term "oxygen permeable film" is a term directed to afilm packaging material surrounding the fresh pork that can permit thetransfer of oxygen from the exterior of the package to the interior ofthe package, when placed in the master bag, at a rate such that theoxygen content in the interior does not change substantially as oxygenis consumed within the package over the lifetime of the packaged pork,typically up to 30 days.

The term "oxygen permeability" or "oxygen permeable film" or packagingmaterial is relates to a material having a permeability of greater thanabout 10,000 cc/m² •day•atm @73° C.; preferably greater than about17,000 cc/m² •day•atm @73° F. Similar permeability values relate to CO₂film properties. Preferred CO₂ permeability ranges from 122,000 cc-CO₂/m2•24 hrs., @73° F. and 100% RH, to 201,500 cc-CO₂ /m2•24 hrs. @73° F.and 100% RH.

The term "extended shelf life" relates to maintaining the quality of thefresh pork in the packaging described in this invention for a period ofat least about 17 days including at least 3 days in the display case.The atmosphere installed in the display unit and in master bagmaintained within the oxygen barrier can be at least 65 vol % oxygen,the balance comprising carbon dioxide. The quality of the meat, thecomponents in the treating solution, the package and the packageatmosphere cooperate to form a superior cut of meat having a true freshmeat appearance, an extended shelf life and highly acceptable consumertaste and tenderness when cooked. The term "appearance" relates both tothe color of the meat and to the absence of visible contaminants orsubstances that would tend to be unacceptable to a retail consumer suchas substantial purge or other accumulated material. "Crust freezing" inthe context of this application relates to lowering the temperature ofthe meat portion to a degree such that the exterior surface of the meatfreezes to a depth of about 16 mm (5/8 inch), preferably 10 mm (3/8inch). Such crust freezing stabilizes the meat for cutting. Fresh meatin the context of this patent application indicates meat that has notbeen frozen except for the crust freezing procedure and the interior ofthe temperature of the meat does not experience a temperature less thanabout -3° C. (27° F.). The term "master bag" refers to a film or filmlaminate or multilayer film container that has sufficient mechanicalproperties to adequately support and contain multiple display units,each unit containing at least one serving portion of fresh pork.Further, the master bag must be an oxygen barrier bag having oxygenpermeability sufficient to maintain the oxygen content in the atmospherewithin the bag for the product lifetime. The term "phosphatesequestrant" typically refers to inorganic phosphate sequesteringmaterials such as phosphate, pyrophosphate, tarpolyphosphate,metaphosphate and other phosphorus based sequestering compositions andequivalents thereof.

The meat packing industry has a continued effort to improve the qualityof meat products, however, there is a continuing need to reduce costs inpackaging while improving shelf life of meat products by reducing growthof bacteria on the cut during manufacturing, storage, distribution andsale. Similarly, a substantial need exists to improve the appearance ofthe meat by maintaining a natural pink color with substantially nopurge, i.e. accumulation of liquid associated with a meat. Furthermaintaining a tender cut after slicing is also desirable. We believe wehave attained several of these goals and other improved aspects of theproduct.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are views of a preferred packaging system of theinvention. The figures show a number of wrapped display units packagedwithin a master bag held within a convenient corrugated paperboardcontainer fitted to the master bag display unit assembly. This productassembly is the result of a process in which the meat is packed in thedisplay units using a non-oxygen barrier wrapping with an artificialatmosphere. The display units are then packaged in an oxygen barriermaster bag with improved atmosphere. The master bag display unitassembly is then used in conjunction with the corrugated paperboard unitwhich promotes ease of production, transportation, storage and retaildisplay. The fresh pork in the display unit has been effectively treatedwith an improved chemical treatment system.

DETAILED DISCUSSION OF THE INVENTION

The invention involves, in part, a significantly improved fresh cut porkproduct that has been attained through a close cooperation betweenpackaging material and aqueous treatment solution. Briefly, the processfor manufacturing a high quality product of the invention involves firstobtaining a primal cut of pork, treating the pork with an aqueoustreatment, optionally slicing the pork, packaging the fresh pork in anoxygen permeable film display unit with an high oxygen atmosphere. Thedisplay unit can be further packaged in an oxygen barrier master bag orcontainer containing a high oxygen atmosphere.

In somewhat greater detail, such primal cuts include large meat unitssuch as fresh pork products including bone-in products and bone-freeproducts such as half carcasses, whole loins, roasts, cuts, chops,ground pork, etc. Primal cuts also include individual serving size cuts(i.e., pork portions weighing 8 oz, 6 oz, 4 oz, etc.) and portions. Suchprimal units can be efficiently treated with aqueous solutions throughpumping or injecting the meat with aqueous treatment solutions. The bonein such a bone-in primal cut can optionally be first sprayed with anaqueous solution of a reducing agent such as ascorbic acid. The pork istreated with an aqueous solution comprising a sodium lactate, aphosphate sequestering agent and a diacetate bacterial growth inhibitor.The aqueous solution is administered by conventional technologyincluding direct injection, vacuum massage, pumping, etc. The meat canbe then crust frozen and tempered at a temperature preferably betweenabout -2° C. and -1° C. (between about 28° F. and 30° F.) The stabilizedmeat from the crust freezing step is optionally sliced into individualserving portions and packaged in a wrapping to form a display unit in apreferred high oxygen atmosphere. Before sealing, the package can beoptionally exposed to a vacuum and is then flushed with a preferredoxygen atmosphere. Such an atmosphere can contain a major proportion ofoxygen and a minor proportion of carbon dioxide. Optionally, at leastone of the display units, with its atmosphere, is placed in a master bagor master container. Preferably, the master bag contains two to twenty,preferably four to ten display units. The master bag is preferablymanufactured from a film or film laminate material. Before sealing themaster bag, the interior of the master bag can exposed to vacuum and isthen flushed with the preferred oxygen atmosphere. One, two or moremaster bags can be placed in a box adapted to contain the master bag(s).After packaging, the materials are maintained at a temperature ofbetween about -2° C. and 0° C. (about 28° to 32° F.) until purchased bythe consumer.

Film Wrapping

Useful materials that act as the wrapping material for the display unitcan include such well known films as polyvinylchloride, polycarbonate,cellophane, polypropylene, polyethylene, polyethylene copolymers such asethylene vinyl acetate copolymers, ethylene methyl acrylate copolymers,ethylene C₃ or higher vinyl monomer copolymers, ionomer films or anyother substantially oxygen gas permeable materials well known in theart. Such a wrapping film may also be constructed of laminates and frommicroporous films having holes either chemically, mechanically orelectrically formed in the layer. The purpose of this display unit is topackage the meat for display to the consumer. Accordingly, the fresh cutpork should be beneficially displayed through the wrapper. Commonly, informing the display units of the invention, one or more fresh cut porkportions are placed on a tray and then wrapped by the film discussedabove. Such trays are generally rigid plastic or foamed plastic unitsthat are about 4 inches×4 inches up through a tray that can be as muchas 12 inches×18 inches. A variety of both thermoplastic andthermoforming materials can be used to form the tray which can be eithertransparent, translucent or opaque. The permeability of the tray is ofno great importance, however, the tray can be perforated to permitexposure to the enclosed display unit atmosphere. The tray is preferablymade of such well known thermoplastics as polyvinylchloride, nylon,fluorocarbon, polyurethane, or composites thereof such aspolyvinylchloride polyolefin laminate, polyvinylchloride saran laminate,polyvinylchloride saran polyolefin laminates, polystyrene, ionomer, highimpact polystyrene, foamed polystyrene, polycarbonate, polyester andothers. Typically, a tray material was selected that can adequatelysupport the weight of the number of fresh pork cuts that can be packagedin the tray. Such trays can be formed with a raised edge having acapacity of retaining the fresh meat within the tray. Further,protuberances on the side of the tray opposite that of the meat canserve as legs or support portions and also can act to interact with thewrapping materials to form a secure seal.

When wrapping the meat, a single sheet of the wrapping material can bewrapped securely around the tray to enclose the meat entirely.Alternatively, the wrapping film can be formed into a cylinder orcylindrical shaped sleeve, the sleeve can then be cut into individualwrapping portions, the meat inserted into the sleeve and the oppositeends of the sleeve sealed using a variety of sealing techniques.Alternatively, one or more of the display units can be inserted into asleeve of the wrapping material, and the individual display units canthen be sealed inside the individual sleeve portions by sealing andcutting the sleeve and display unit after the controlled atmosphere isinstalled. A variety of known wrapping techniques can be used forwrapping the display unit with the non-barrier film.

Briefly, the packaged fresh meat of the invention involves at least onedisplay unit containing at least one wrapped portion of sliced freshmeat. A wide variety of wrapping materials are useful in forming thedisplay unit of the invention. Wrapping materials are typically filmmaterials having a thickness of less than about 0.2 millimeters.Preferred wrapping materials have some elasticity or stretchiness to thefilm that aids in wrapping and sealing the fresh pork products. Thepreferred film is transparent, very flexible, and is not a substantialbarrier to the passage of oxygen.

The atmosphere in the display unit and in the master bag is initiallyobtained from the ambient atmosphere and is about 78 vol % nitrogen(N₂), about 21 vol % oxygen (O₂) with the balance argon (Ar) and othertrace gases. The ambient atmosphere within the display unit is replacedwith an artificial oxygen atmosphere. The atmosphere adjustment in thepackaging method of the invention can be obtained by simply directing aflow of the artificial atmosphere into the partially closed displayunit. A partially closed display unit comprises at least one fresh cutpork portion and the wrapping material sealed on one, two or three sidesof the unit. Alternatively, the display unit can be virtually completelysealed leaving only a small unsealed opening for atmospheremodification. In adjusting the atmosphere, a flow of the artificialatmosphere can be initiated sweeping the ambient atmosphere from thepackage until it is completely replaced with the artificial atmosphere.Alternatively, the interior of this display unit can be exposed to avacuum which removes the ambient atmosphere from the package. Once theambient atmosphere is removed from the package, the atmosphere can bereplaced with the artificial atmosphere. In such a process, little ofthe artificial atmosphere is wasted because the introduction of theartificial atmosphere replacing the ambient atmosphere leaves little ofthe artificial atmosphere to be released from the display unit duringsealing operations subsequent to atmosphere modification.

Preferred atmosphere for the packaged pork of this invention include ahigh oxygen atmosphere comprising at least 65 mole % oxygen. With a highoxygen atmosphere a variety of packaging materials can be used for thedisplay unit. In the instance that the display unit is distributed asis, the display unit can be covered with a high O₂ /high CO₂ barrierfilm. In the instance that the display unit containing a high oxygenatmosphere is distributed in a master bag or master container containinga high oxygen atmosphere surrounding the display unit, an oxygenpermeable film can be used to prepare the display unit. The oxygenpermeable film permits oxygen from the master container or bag topenetrate the film and replenish any oxygen consumed within the displayunit package.

Treatment Compositions

We have found that the treatment chemicals cooperate with an effectivepackaging system and atmosphere for maintaining the fresh appearance ofthe pork. Prior to packaging the fresh cut pork portions, a primal unitof pork is treated with an aqueous solution. The preferred aqueoussolution of the invention comprises an alkali metal lactate component, aphosphate sequestrant component, and a diacetate microbial growthinhibitor/flavor enhancer composition. These components cooperate topreserve the hemoglobin and myoglobin pigments in the meat, stabilizethe cell structure of the meat, prevent purge from the meat and inhibitthe growth of microorganisms in or on the meat surface. The aqueoustreatment solution of the invention can be incorporated in the meatprior to slicing into individual serving size portions by a vacuummassage, an injection, pumping the meat using a vein pumping system andothers well known in the art. We have found the treatment solution ofthe invention increases the flavor and tenderness of the pork.

The aqueous solution used in treating the primal cuts of the inventioninclude a major proportion of an aqueous diluent in combination withthree active constituents. The first useful material in the treatmentsolution is an alkali metal lactate composition. Sodium and potassiumlactate compositions, and equivalents thereto, are preferred in thisinvention. In this invention the lactate salt is used to maintain thewater content of the meat. Lactate ties up water and preventsaccumulation of purge in the package. Further, sodium lactate cooperateswith the other ingredients in the treatment solution to obtain humectantproperties, pH control and flavor enhancement. The useful concentrationof lactate salt in the treatment solution can vary over a wide range.Useful concentrations of lactate salt can be from about 5 to 25 wt %,preferably 10 to 12 wt % in the aqueous treatment solution. The treatedpork contains, after treatment with the aqueous solution, about 1 to 5wt %, preferably 1 to 3 wt % of lactate (measured as sodium lactate)based on the pork product.

The second active component of the aqueous treatment solution is aphosphate sequestering or chelating agent. The sequestering agent is achemical composition capable of bonding certain divalent and trivalentmetal ions present in the meat product. A phosphate chelating agent iscapable of tying up iron (Fe²⁺, Fe³⁺), zinc, copper, calcium, magnesiumand other typically di- or trivalent metal species. Several effectivephosphate sequestering agents are known to form chelation complexes withsuch metal ions. Such phosphate sequestering agents can containphosphate species such as phosphate or orthophosphate (e.g., PO₄ ⁻³,HPO₄ ⁻², etc.); pyrophosphate species such as P₂ O₇ ⁻³ ;tripolyphosphate O--PO₂ --O--PO₂ --O--PO₃ ⁻⁵ ; hexametaphosphate, cycliccondensed phosphates, including mixtures and equivalents thereto, etc.The phosphate sequestrant materials complex the trivalent metal ions inthe preserved myoglobin and help to maintain the high quality appearanceof the meat. The phosphate chelating agent also provides tenderizing andtexturizing properties.

The primary sequestrant used in the invention is a phosphatesequestrant, however, other food grade sequestrants can be combined withthe phosphate sequestrants including citric acid, tartaric acid,ethylenediamine tetracetate and other known and improved sequesteringagents. The amount of sequestering agent in the treatment solution isabout 0.5 to 10 wt % based on the aqueous treatment solution. Thetreated pork contains about 0.1 to 0.5 wt.% of the phosphate sequestrantbased on the pork product.

The aqueous treatment solution can contain a diacetate agent that hasthe capacity of reducing bacterial growth. Such a material has a strongimpact on the microbial populations in the fresh meat, but also shouldhave other functions. We have found that an alkali metal diacetatematerial can act as a buffer, can inhibit the growth of unwantedmicroorganisms in and on the meat product, and provides a desirableflavor enhancement to the meat. The preferred diacetate material, sodiumhydrogen diacetate also known as sodium diacetate, CAS#: 126-96-1!, is amolecular compound having the formula:

    CH.sub.3 --CO.sub.2 •X•CH.sub.3 --CO.sub.2 H•xH.sub.2 O

wherein X is an alkali metal cation such as sodium (Na⁺) or potassium(K⁺) and x represents known hydration amounts. The alkali metaldiacetate, and equivalents thereto, can be present in the aqueoustreatment solution over a broad range of concentrations including about0.05 to 5 wt % of the growth inhibitor based on the aqueous treatmentsolution. The treated pork product can contain up to about 0.2 wt %alkali metal diacetate, preferably about 0.01 to 0.2 wt % alkali metaldiacetate, most preferably for reasons of improved taste and microbialsupression, about 0.05 to 0.1 wt % alkali metal diacetate in the porkproduct. After treatment, the weight of the pork will be preferablyincreased about 5 to 25 wt % and will contain about 1.0 to 2.0 wt % ofthe alkali metal lactate, about 0.2 to 0.5 wt % of the phosphatesequestrant and about 0.01 to 0.10 wt % of the diacetate bacterialgrowth inhibitor/flavor enhancer.

In treating the fresh pork with the aqueous treatment solution of theinvention, the meat is typically treated using conventional techniquesinvolving the introduction of the aqueous solution into the meat portionin a sufficient volume of the treatment solution to affect theproperties of the material. After treatment, the weight of the pork willbe increased about 0.5 to 25 wt %. The aqueous treating solution of theinvention is typically made by combining the ingredients in an aqueoussolution. The preferable pH of the treatment solution should bemaintained between about 5.5 and 6.5.

As an optional step, either before or after the use of the aqueoustreatment solution, the intact fresh primal cut containing exposed bonecan be sprayed, i.e., the exterior of the chine, or bone-in meat, can betreated with an aqueous solution of a food grade reducing agentmaterial. The aqueous solution of the reducing agent or compound causesthe bone to retain its red color and to have a fresh appearance over anextended time period. Such treatment solution can be manufactured bycombining the reducing agent with water in the appropriateconcentrations. Preferred concentration for the reducing agent is about1 to 3 wt % of reducing agent. The preferred food grade reducing agentfor use in this invention is ascorbic acid or isoascorbic acid and thealkali metal salts thereof. Potassium and sodium ascorbate arepreferred. An amount of the spray material is added to the exposed bonesuch that the exterior surfaces of the bone is fully contacted with thespray solution.

After the meat has been subject to the chemical treatments discussedabove, the meat can be crust frozen, if desired before furtherprocessing, and tempered prior to slicing. For the purposes of thisinvention, crust freezing indicates that the meat is subjected to atemperature below about -18° C. to -24° C. (about 0° F. to -10° F.) fora sufficient period of time to freeze a crust layer in the meat tostabilize the meat for slicing. The depth of the frozen portion of themeat should be no more than about 16 millimeters, preferably less than12 millimeters. In performing the crust freezing process, the meat isnot slowly cooled to freeze the crust, but is quickly frozen at lowtemperatures for a sufficient period of time to form the frozen crust.After the frozen crust is obtained, the meat is tempered at atemperature below freezing, but close to the freezing point of the meatto aid in stable, cooled, firm, and easily sliced cut. Accordingly, inthe preferred procedure of the invention,. the meat is quick frozen at atemperature that is less than about -12° C. (10° F.), less than -17° C.(0° F.). Preferably a temperature of less than about -23° C. (-10° F.)to form the crust and the meat is then tempered at a temperature betweenabout -3° C. and 0° C. (about 26° F. to 31° F.). However, the resultingmeat is not substantially degraded by the freezing cycle because largedamaging ice crystals are not formed in the majority of the meat duringthe crust freezing process. In order to form the preferred crustfreezing process, the meat is taken to a chamber having appropriatecoolants. Depending on the temperature of the cooled chamber and thecoolants, the meat is maintained within the freezing chamber for only alimited amount of time. At about -24° C. (-10° F.), the meat should beplaced in the cooling chamber for about 20-150 minutes. At about -17° C.(0° F.) the meat can be left in the cooling chamber about 50-180minutes. Little experimentation is needed to establish the time requiredfor the crust freezing to occur at appropriate crust freezingtemperatures.

In order to obtain a crustal frozen and tempered cut, the crust frozenmeat is maintained in a cooling chamber at a temperature between about-3° C. and 0° C. (26° F. and 31° F.) for a sufficient period of time tocool the meat to a uniform temperature of about -3° C. to -0.5° C. (28°F.-29° F.). The uniformly tempered meat is prepared in serving portionsthat can comprise a half carcass, a whole loin, 2-3 lb. roasts, chops,various cuts, ground pork, etc. Such portions can have a weight ofgreater than 100 lbs., can be less than 20 lbs., can be between about 2to 16 ounces, preferably about 4 to 8 ounces. After slicing, the meat ispackaged in a typical display unit within a closed film package.Preferably, the meat is introduced into a receptacle or tray and themeat and receptacle are then wrapped with a non-barrier film asdiscussed above. Further, the tray can contain typical absorbing unitsthat can absorb purge or other liquid materials that can exist with ameat product. Once the display units are formed they are quickly placedin a master bag for storage, transportation, distribution and retailsale purposes. The master bag is typically made of a film material thatacts as a barrier to the enclosed atmosphere. Such barrier films cancomprise a relatively thick single layer of a polymer forming filmmaterial such as those described above in the portion relating to thewrapping of the display units. However, the preferable barrier materialhas two, three, four, five or more layers of polymeric materials, layersor coatings that cooperate to form the oxygen or CO₂ barrier. Amultilayer barrier material of the invention can be made from a varietyof thermoplastic materials that act as good barriers to the passage ofoxygen and other relevant gasses. Such materials includepolyvinylchloride, polyvinylidene chloride and copolymers thereof,ethylenevinyl alcohol copolymers, acrylonitrile barrier polymers,poly(ethylene-terephthalate), polypropylene, high density polyethyleneand others. The multilayer barrier structures of the invention can bemade by coextrusion, lamination, coating or combination of suchtechniques. The combinations may result in blends that are eithermiscible or immiscible. A preferred film is a Cryovac P869 film with athickness of 3.0 mil and a permeability of 145.3 cc-O₂ /m² •24 hrs. @73°F. and 100% RH. In any case, the blend seeks to combine the bestproperties of two or more materials to enhance the oxygen barrier valueof the final structure. Using a layered structure, high barriermaterials that do not have substantial mechanical stability can becombined with materials that are not as good a barrier to oxygen, carbondioxide, etc. permeation but are high strength materials. Further, themechanically robust film can then act as a substrate for layers ofmaterials formed using coating or extrusion techniques. One preferredlayered barrier film uses an internal skin layer, a barrier layer and anexternal skin layer. The barrier layer is tied to the external and theinternal skin layer using an adhesive tie layer to maintain theintegrity of the five layer barrier corkscrewed shape. Using suchmultilayer techniques, a thin barrier layer can be used conservingvaluable materials. In such constructions, a thin layer of the barrierpolymer can be coated on a substrate. For example, a water born latexcan be used to coat paper or a polymer such as polypropylene orpolyethylene terephthalate. Commonly two coats are applied to give atotal barrier thickness of 5 microns, up to 10 microns or more. Twocoats are useful so that minor holes in the first layer can be coveredwith the second layer. Adhesion of the coating is important for allsubstrates and it is important that the material does not soak into thesubstrate (there is substantial hold out of the coating on the firstlayer). When the surface energy or the nature of the materials aresubstantially different, the substrate or layer must receive a surfacetreatment prior to coating. A typical application is avinylidenechloride copolymer latex on an oriented polypropylene film.One significant commercial application of a solvent coating on a filminvolves a solution of polyvinylidenechloride resin dissolved in a polarsolvent coated onto a cellophane or polyethylene terephthalate film.Also, ethylene-vinyl alcohol polymers are potentially applicable forsolvent coating. Certain inorganic coatings on polymers are also knownto have substantial potential to enhance barrier properties, however, atthis time commercial development of inorganic layers are notsignificant. Further, in any layer manufactured in the barrier polymer,a polymer blend or alloy can be used. Such blends involve polymers whichare soluble or at least dispersible. Further, the coating solutions usedto form any of the barrier coatings of the application can contain twoor more polymers which tend to be more compatible because of thesolution coating process.

The resulting barrier films typically have a greater thickness thansingle layer films discussed above. The thickness of such films canrange from 1000 μm to about 2000 μm. The important barrier parameter forthe master bag film is oxygen permeability. The oxygen permeability ofthe master bag film should be sufficient such that the oxygen content ofthe master bag does not drop substantially during transportation,distribution, and storage up to final retail sale. The oxygen atmospherewithin the master bag helps to maintain the quality appearance of themeat. Accordingly, during the presence of the display units within themaster bag, the oxygen content of the atmosphere within the bag does notdrop more than about 5 vol % due to consumption of oxygen by thecontents of the bag and through permeation of oxygen from the bag.

As in the packaging of the fresh cut pork in the display units, thedisplay units are introduced into the master bag and the atmospherewithin the master bag is adjusted to the required proportions of oxygen.Similarly, the ambient atmosphere within the master bag can be removedby exposure of the internal spaces within the master bag to a vacuum.Once the ambient atmosphere is removed, the artificial atmosphere canthen be introduced into the bag ensuring that the atmosphere containsthe desirable proportion of oxygen and carbon dioxide required tomaintain the quality of the cut meat. Once the desired atmosphere isobtained, the bag is sealed and is then distributed into the retailmarket. The handling of the display units within the master bag of theinvention is often made significantly easier by placing the master bagand display units in a corrugated paperboard tray which is sized toaccept two, four, six, eight, ten, twelve or more display unitscontained within the master bag. Alternatively, the display units can beintroduced into the corrugated paperboard tray, the display units andpaperboard tray can be then introduced into the barrier bag foratmosphere adjustment prior to sealing. In such an assembly, the displayunits can be stacked into layers having two or three layers of displayunits, however, any substantial stacking greater than two or three unitscan reduce the quality of the cut pork portions at the bottom of thestack. Accordingly, the units are stacked in preferably two or threeunits at the most.

To aid in storage, distribution, etc. the master bag units can beintroduced into a frame that can support the weight of the unit butmaintains a separation of the units during handling. Such units can bewrapped in a pallet arrangement and stored and distributed in that formuntil delivered to a retail location.

The above description of the treated fresh cut pork portions, thewrapping, the atmosphere and the treatment solutions provide a basis forunderstanding the metes and bounds of the invention. The followingexamples and data further illustrate the invention and contain a bestmode.

We have conducted a series of tests. The primary objective of thetesting is to produce treated boneless pork cuts that have minimalpurge, color stability, increased tenderness and a total shelf life(including three days in the display case) of at least seventeen days ormore. Sample preparation was accomplished as follows. Four center cutboneless pork loins for each treatment were pumped 112% with one of fourdifferent solutions. All loins were placed on a rack and were crustfrozen in a blast freezer (0° F.) for 1.5 hours and were then temperedin a cooler overnight to a uniform temperature of 28°-29° F. Thetempered loins were sliced into 5/8 inch chops and placed on styrofoamtrays. The trays were overwrapped with Cryovac® SSD330 shrink filmOVERWRAP FILM: CRYOVAC® SSD-330 2.4 Mils Thick (60 Gauge) with apermiability of 10,000 cc-O₂ /m² /24 Hrs@100% RH/73° F. and 39,000cc-CO₂ /M² /24 Hrs@100% RH/73° F.! on a packaging machine. The packageswere placed in a cryovac barrier master bag MASTER BAG:CRYOVAC P869 3.0Mils Thick with 145.3 cc-O₂ /m² /24 Hrs@100% RH/73° F! and backflushedwith a gas mixture of 80% oxygen/20% carbon dioxide. The product wasthen boxed. The boxes were held in a 28° F. cooler for 24 hours and werethen moved to a 36°-38° F. cooler for an additional 11 days of storage.After 12 total days of storage (from date of pack) in the master bag,the packages were removed from the master bags and were placed in a36°-38° F. display case. Samples from each of the four treatments weresent to the lab. Samples from each treatment were again sent to the labafter two days and four days in the display case. All test samples werepackaged and backflushed in barrier master bags according to thespecifications shown below.

A summary of the results of the microbial testing is shown in thefollowing table:

    ______________________________________                                        Injected Boneless Loins                                                       TREATMENT                                                                     Sampled 12/04   TPC     PSYCHRO                                               ______________________________________                                        1-1               330    3500                                                 1-2               560    9300                                                 1-3               70     13000                                                1-4               180    32000                                                2-1             1.2M    3.0M                                                  2-2             300000  1.5M                                                  2-3             130000  2.3M                                                  2-4             125000  1.4M                                                  3-1             330000  150000                                                3-2              31000  340000                                                3-3              45000  3.1M                                                  3-4              43000  720000                                                4-1             5.9M    85M                                                   4-2             4.6M    30M                                                   4-3             4.3M    5.2M                                                  4-4             400000  3.1M                                                  ______________________________________                                    

TREATMENT

1-1 to 1-4: Sodium tri-polyphosphate (0.5%), sodium lactate (1.5%),sodium diacetate (0.1%).

2-1 to 2-4: Sodium tri-polyphosphate (0.5%), sodium lactate (1.35%),potassium lactate (0.15%).

3-1 to 3-4: Sodium tri-polyphosphate (0.5%), potassium lactate (2.0%).

4-1 to 4-4: Cure gel (phosphates+hydrolyzed gelatin) (1.0%).

    ______________________________________                                        Samp 12/08     TPC     PSYCHRO                                                ______________________________________                                        1-1              180    50000                                                 1-2              340    34000                                                 1-3            170000  160000                                                 1-4            190000  180000                                                 2-1             21M     22M                                                   2-2            7.4M    7.3M                                                   2-3            5.7M    7.7M                                                   2-4            4.4M    4.2M                                                   3-1            940000  1.4M                                                   3-2            1.0M    630000                                                 3-3            5.8M    6.2M                                                   3-4            780000  410000                                                 4-1             40M     68M                                                   4-2             15M     13M                                                   4-3            5.2M    5.1M                                                   4-4            3.7M    5.3M                                                   ______________________________________                                         TPC = TOTAL MESOPHILIC PLATE COUNT/GRAM                                       PSYCHRO = PSYCHROPHILLIC BACTERIA/GRAM                                        M = ×10.sup.6 (MILLIONS)                                           

This data shows that, under similar atmospheric conditions, the use ofthe treatment of the invention comprising lactate, a phosphatesequestrant and sodium diacetate, resulted in substantially reducedmicrobial growth. The pork had reduced purge and was a high qualityconsumer offering. This treatment solution will improve pork and reducemicrobial growth under other atmospheres and packaging alternatives.

The test data was obtained using the following laboratory protocols:

Aerobic Plate Count

BAM 8th Edition 1995, Aerobic Plate Count, Method 3.01

Psychrophilic Count

Compendium of Methods for the Microbiological Examination of Foods 3rdEdition, 1992, Chapter 9, pp. 153-168.

pH

USDA Analytical Chemistry Laboratory Guidebook, 1993, Method PHM.

TBA

Journal American Oil Chemists Society, Jan 1960, Vol XXXVII, No. 1, pp.44-48.

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

We claim:
 1. A process for packaging fresh pork to obtain improvedappearance and extended shelf life, which process comprises:(a) treatingfresh pork with an aqueous solution, comprising a major proportion ofwater and an alkali metal lactate agent, a phosphate sequestrant and analkali metal diacetate microbial growth inhibitor, said aqueous solutionused in an amount sufficient to increase the weight of the pork up toabout 125 wt-% of the original weight, to produce a treated porkcomprising about 1 to 5 wt % of alkali metal lactate, about 0.1 to 0.5wt % of a phosphate sequestrant and about 0.01 to 0.2 wt % of adiacetate microbial growth inhibitor, the percentages based on the pork;and (b) packaging the treated pork, in a closed film package, to form adisplay unit.
 2. The process of claim 1 wherein the pork comprisesbone-in-pork or a boneless pork.
 3. The process of claim 2 wherein thepork comprises bone-in pork and the exterior of the bone is contactedwith an aqueous solution of ascorbic acid or a salt thereof, prior totreating with the aqueous solution.
 4. The process of claim 1 whereinthe pork is crust frozen prior to packaging.
 5. The process of claim 1wherein the treated pork is crust frozen at a temperature of about -3°C. to 0.5° C. and wherein the packaged fresh pork is maintained at atemperature of less than about 0° C.
 6. The process of claim 5 whereinthe crust frozen pork is tempered and the packaged fresh pork ismaintained at a temperature of between about -3° C. and 0° C.
 7. Theprocess of claim 1 wherein the aqueous solution contains 0.1 to 15 wt-%soluble solids.
 8. The process of claim 1 wherein the sequestrantcomprises sodium tripolyphosphate, sodium pyrophosphate or mixturesthereof.
 9. The process of claim 1 wherein the pork is sliced prior topackaging.
 10. The process of claim 1 wherein the diacetate microbialgrowth inhibitor comprises sodium diacetate.
 11. The process of claim 10wherein the sodium diacetate comprises CH₃ CO₂ Na•CH₃ CO₂ H or itshydrated form.
 12. The process of claim 1 wherein the lactate agentcomprises sodium lactate.
 13. The process of claim 1 wherein the displayunit comprises a thermoplastic foam tray, at least one serving portionof pork and a transparent film.
 14. The process of claim 1 wherein theweight of the fresh pork is increased through the addition of a pumpingsolution up to about 120 wt %.
 15. The process of claim 1 wherein thetreated pork is divided into forming serving portions, the servingportions are packed in a closed oxygen permeable package to form adisplay unit with an enhanced oxygen atmosphere in the closed package,and at least one display unit is packed in a closed oxygen barriercontainer having an internal atmosphere comprising an enhanced oxygenatmosphere.
 16. The process of claim 15 wherein the barrier container isa barrier bag.
 17. The process of claim 16 wherein the barrier bag hasan oxygen permeability of less than about 200 cc-O₂ /m² •day•atm. 18.The process of claim 15 wherein the display package comprises athermoplastic foam tray, at least one serving portion of pork and afilm.
 19. The process of claim 15 wherein the display package comprisesa thermoplastic foam tray, at least one serving portion of pork and apolyvinylidene chloride film.